Glass fibers intended for incorporation as reinforcing elements in articles fabricated from various matrix materials, such as polymeric or resinous materials, are usually provided with a light-weight size coating to protect the fibers from damage by abrasion during processing and fabrication and/or to enhance the reinforcing interaction between the fibers and the matrix material. Such size coatings typically comprise a film-forming polymeric or resinous component, a lubricant and a glass-resin coupling agent such as a partially hydrolyzable organosilane or hydrolysate thereof.
Such size coatings are usually deposited on the glass fibers during their production, which is ordinarily by attenuation of a plurality of streams of molten glass issuing from a reservoir through a corresponding plurality of orifices in a so-called bushing and solidification of the attenuated filaments by cooling. The coating is typically applied to the fibers as a liquid solution or dispersion in a volatile medium, from which the ultimate size coating is deposited on the fibers by evaporation of the medium and any other volatile components either before or after the fibers have been collected into a package as by winding onto a suitable collet.
Among the film-forming components of sizing compositions that have been employed are epoxy resins, especially where the fibers are to be used for reinforcing articles made from epoxy resins such as by winding essentially continuous multi-filament glass fiber strands about a suitable form and impregnating with a curable resin composition and then curing the matrix resin to produce a glass fiber reinforced article such as a pipe or a tank. Both dilute solutions containing epoxy resin film-formers in volatile solvents such as diacetone alcohol and dilute emulsions of epoxy resin film-formers in aqueous media have beem employed as sizing compositions for glass fibers, usually with the inclusion of other components such as an organosilane or other coupling agent and a lubricant such as mineral oil.
While a number of organosilanes or hydrolysates thereof, either alone or in varius mixtures, have been employed as coupling agents in such sizing compositions, the advantages of employing the silane component employed in the dilute aqueous epoxy resin emulsion sizing compositions of the present invention have not heretofor been appreciated in the art.